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</a></div> <!----></nav>  <ul class="sidebar-links"><li><a href="/docs/js/" aria-current="page" class="sidebar-link">介绍</a></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading open"><span>JavaScript</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/docs/js/base/type-of-data.html" class="sidebar-link">JS 的数据类型</a></li><li><a href="/docs/js/base/object.html" class="sidebar-link">JS 对象的常用属性</a></li><li><a href="/docs/js/base/function.html" class="sidebar-link">函数 &amp; 原型链</a></li><li><a href="/docs/js/base/dom-api.html" class="sidebar-link">DOM API 总结</a></li><li><a href="/docs/js/base/node-api.html" class="sidebar-link">节点 API 总结</a></li><li><a href="/docs/js/base/node-list.html" class="sidebar-link">节点中的伪数组</a></li><li><a href="/docs/js/base/dom-operate-across-threads.html" class="sidebar-link">DOM 操作跨线程</a></li><li><a href="/docs/js/base/create-jquery.html" aria-current="page" class="active sidebar-link">jQuery 中的链式操作</a></li><li><a href="/docs/js/base/plugin.html" class="sidebar-link">JavaScript 插件 / 库</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>ES6</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/docs/js/es6/scope.html" class="sidebar-link">作用域</a></li><li><a href="/docs/js/es6/new-object.html" class="sidebar-link">新版对象</a></li><li><a href="/docs/js/es6/anatomy-assignment.html" class="sidebar-link">参数处理 &amp; 解构赋值</a></li><li><a href="/docs/js/es6/new-string.html" class="sidebar-link">新版字符串</a></li><li><a href="/docs/js/es6/module-use.html" class="sidebar-link">ES6 模块化</a></li><li><a href="/docs/js/es6/promise-usage.html" class="sidebar-link">Promise</a></li><li><a href="/docs/js/es6/await-and-async.html" class="sidebar-link">async 和 await 的用法</a></li><li><a href="/docs/js/es6/symbol-iterate-generate.html" class="sidebar-link">Symbol &amp; 迭代器 &amp; 生成器</a></li><li><a href="/docs/js/es6/arrow-function.html" class="sidebar-link">箭头函数</a></li><li><a href="/docs/js/es6/new-api.html" class="sidebar-link">ES6 新增 API</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>JavaScript 进阶</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/docs/js/part/ajax-use.html" class="sidebar-link">AJAX</a></li><li><a href="/docs/js/part/cross-domain.html" class="sidebar-link">跨域 &amp; CORS &amp; JSONP</a></li><li><a href="/docs/js/part/browser-storage.html" class="sidebar-link">浏览器模型</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>JS 小记</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/docs/js/note/project.html" class="sidebar-link">JavaScript 搭建项目</a></li><li><a href="/docs/js/note/js-garbage.html" class="sidebar-link">JS 的缺陷</a></li><li><a href="/docs/js/note/setInterval-a-setTimeout.html" class="sidebar-link">使用 setTimeout 实现 setInterval</a></li><li><a href="/docs/js/note/array-deduplica.html" class="sidebar-link">数组去重</a></li><li><a href="/docs/js/note/download-file.html" class="sidebar-link">使用 JS 下载文件</a></li><li><a href="/docs/js/note/top-nav.html" class="sidebar-link">设置导航动态显示 / 隐藏</a></li><li><a href="/docs/js/note/anchor-transition.html" class="sidebar-link">JS 实现点击锚点过渡效果</a></li><li><a href="/docs/js/note/data-list.html" class="sidebar-link">数据处理</a></li></ul></section></li></ul> </div></div><div class="el-scrollbar__bar is-horizontal"><div class="el-scrollbar__thumb" style="width:0;transform:translateX(0%);ms-transform:translateX(0%);webkit-transform:translateX(0%);"></div></div><div class="el-scrollbar__bar is-vertical"><div class="el-scrollbar__thumb" style="height:0;transform:translateY(0%);ms-transform:translateY(0%);webkit-transform:translateY(0%);"></div></div></div></aside> <main class="page"> <div class="re-page-top"><h1 class="title"><span>jQuery 中的链式操作</span></h1> <div class="re-page-index"><div class="page-index-title"><span class="open-catalog"><svg aria-hidden="true" class="icon arrow-right"><use xlink:href="#icon-bold-right"></use></svg> <span class="text">目录</span></span></div> <div class="page-index-content"><div class="page-catalog" style="display:none;"><div class="synopsis-wrap"><ul class="synopsis-ul"><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#实现-jquery-的-addclass-功能" class="synopsis-link">实现 jQuery 的 addClass 功能</a><ul class="synopsis-ul"><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#封装" class="synopsis-link">封装</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#链式操作" class="synopsis-link">链式操作</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#简化封装" class="synopsis-link">简化封装</a></li></ul></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#实现-jquery-的-find-功能" class="synopsis-link">实现 jQuery 的 find 功能</a><ul class="synopsis-ul"><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#封装-2" class="synopsis-link">封装</a></li></ul></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#链式操作-2" class="synopsis-link">链式操作</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#简化命名" class="synopsis-link">简化命名（$）</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#实现-end-返回之前操作的元素" class="synopsis-link">实现 .end()（返回之前操作的元素）</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#实现-get-、each-、parent-、children" class="synopsis-link">实现 get()、each()、parent()、children()</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#实现-appendto" class="synopsis-link">实现 appendTo()</a></li><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#命名风格" class="synopsis-link">命名风格</a><ul class="synopsis-ul"><li class="synopsis-li"><a href="/docs/js/base/create-jquery.html#拓展" class="synopsis-link">拓展</a></li></ul></li></ul></div></div></div></div></div> <div class="theme-default-content content__default"><h2 id="实现-jquery-的-addclass-功能"><a href="#实现-jquery-的-addclass-功能" class="header-anchor">#</a> 实现 jQuery 的 addClass 功能</h2> <p>假设给以下 div 添加 class</p> <div class="language-html extra-class"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
</code></pre></div><h3 id="封装"><a href="#封装" class="header-anchor">#</a> 封装</h3> <div class="language-js extra-class"><pre class="language-js"><code>window<span class="token punctuation">.</span><span class="token function-variable function">jQuery</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">selector</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token keyword">const</span> elements <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selector<span class="token punctuation">)</span>
    <span class="token keyword">const</span> api <span class="token operator">=</span> <span class="token punctuation">{</span>
        <span class="token function-variable function">addClass</span><span class="token operator">:</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">className</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
            <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">let</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span> i<span class="token operator">&lt;</span>elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
                elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span>classList<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>className<span class="token punctuation">)</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">return</span> api
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> api
<span class="token punctuation">}</span>
</code></pre></div><h3 id="链式操作"><a href="#链式操作" class="header-anchor">#</a> 链式操作</h3> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">const</span> demo <span class="token operator">=</span> <span class="token function">jQuery</span><span class="token punctuation">(</span><span class="token string">'.test'</span><span class="token punctuation">)</span>
<span class="token comment">// 给 test 追加 red blue yellow</span>
demo<span class="token punctuation">.</span><span class="token function">addClass</span><span class="token punctuation">(</span><span class="token string">'red'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">addClass</span><span class="token punctuation">(</span><span class="token string">'red'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">addClass</span><span class="token punctuation">(</span><span class="token string">'blue'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">addClass</span><span class="token punctuation">(</span><span class="token string">'yellow'</span><span class="token punctuation">)</span>
</code></pre></div><h3 id="简化封装"><a href="#简化封装" class="header-anchor">#</a> 简化封装</h3> <p>因为可以直接 return 一个对象，所以 api 这个名字可以省略，而由于函数的 this 指向它外面的对象，所以 addClass return 的 this 就是之前的 &quot;api对象&quot;</p> <div class="language-js extra-class"><pre class="language-js"><code>window<span class="token punctuation">.</span><span class="token function-variable function">jQuery</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">selector</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token keyword">const</span> elements <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selector<span class="token punctuation">)</span>
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
        <span class="token function-variable function">addClass</span><span class="token operator">:</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">className</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
            <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">let</span> i<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span> i<span class="token operator">&lt;</span>elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
                elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span>classList<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>className<span class="token punctuation">)</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">return</span> <span class="token keyword">this</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="实现-jquery-的-find-功能"><a href="#实现-jquery-的-find-功能" class="header-anchor">#</a> 实现 jQuery 的 find 功能</h2> <p>假设给以下所有的 test 的子元素添加 'red' 类名</p> <div class="language-html extra-class"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>1<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>2<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>3<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>1<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>2<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>test<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>item<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>1<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
</code></pre></div><h3 id="封装-2"><a href="#封装-2" class="header-anchor">#</a> 封装</h3> <p>在 window.jQuery 中添加一个新的 return 方法</p> <div class="language-js extra-class"><pre class="language-js"><code>window<span class="token punctuation">.</span><span class="token function-variable function">jQuery</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">selectorOrArray</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">let</span> elements
    <span class="token comment">/* 判断 selectorOrArray 如果是字符串说明是选择器，就根据选择器做dom处理 */</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">typeof</span> selectorOrArray <span class="token operator">===</span> <span class="token string">'string'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selector<span class="token punctuation">)</span>
    <span class="token comment">/* 如果是数组说明是通过.find返回的。就直接返回该数组 */</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>selectorOrArray <span class="token keyword">instanceof</span> <span class="token class-name">Array</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> selectorOrArray
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
        <span class="token function">addClass</span><span class="token punctuation">(</span><span class="token parameter">className</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span>classList<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>className<span class="token punctuation">)</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">return</span> <span class="token keyword">this</span>
        <span class="token punctuation">}</span><span class="token punctuation">,</span>
        <span class="token comment">/**
         * 接收一个字符串，遍历字符串中的每一项，
         * 将它们追加到一个新的数组中，并在返回的 jQuery 中传入这个数组。
         */</span>
        <span class="token function">find</span><span class="token punctuation">(</span><span class="token parameter">selector</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">let</span> array <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token comment">/* 此处 Array.from 表示将伪数组转为数组 */</span>
                <span class="token keyword">const</span> childElements <span class="token operator">=</span> Array<span class="token punctuation">.</span><span class="token function">from</span><span class="token punctuation">(</span>elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selector<span class="token punctuation">)</span><span class="token punctuation">)</span>
                <span class="token comment">/* concat 表示数组中追加项(可以是一个或多个) */</span>
                array <span class="token operator">=</span> array<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>childElements<span class="token punctuation">)</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">return</span> <span class="token function">jQuery</span><span class="token punctuation">(</span>array<span class="token punctuation">)</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="链式操作-2"><a href="#链式操作-2" class="header-anchor">#</a> 链式操作</h2> <p>给所有名为 test 的所有子元素追加一个 'red' 类名</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> demo <span class="token operator">=</span> window<span class="token punctuation">.</span><span class="token function">jQuery</span><span class="token punctuation">(</span><span class="token string">'.test'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">'.item'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">addClass</span><span class="token punctuation">(</span><span class="token string">'red'</span><span class="token punctuation">)</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>demo<span class="token punctuation">)</span>
</code></pre></div><h2 id="简化命名"><a href="#简化命名" class="header-anchor">#</a> 简化命名（<code>$</code>）</h2> <p>只需要在封装时加入以下代码，就可以使用 <code>$('.test')</code> 的方式操作元素。</p> <div class="language-js extra-class"><pre class="language-js"><code>window<span class="token punctuation">.</span>$ <span class="token operator">=</span> window<span class="token punctuation">.</span>jQuery
</code></pre></div><h2 id="实现-end-返回之前操作的元素"><a href="#实现-end-返回之前操作的元素" class="header-anchor">#</a> 实现 <code>.end()</code>（返回之前操作的元素）</h2> <p>代码就是在之前的基础上添加以下高亮的代码。</p> <div class="language-js extra-class"><div class="highlight-lines"><br><br><br><br><br><br><div class="highlighted"> </div><div class="highlighted"> </div><div class="highlighted"> </div><br><br><div class="highlighted"> </div><br><br><br><br><br><br><br><br><br><br><br><br><br><br><div class="highlighted"> </div><br><br><br><br><div class="highlighted"> </div><br><br><br><br></div><pre class="language-js"><code>window<span class="token punctuation">.</span><span class="token function-variable function">jQuery</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">selectorOrArray</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">let</span> elements
    <span class="token comment">/* 判断 selectorOrArray 如果是字符串说明是选择器，就根据选择器做dom处理 */</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">typeof</span> selectorOrArray <span class="token operator">===</span> <span class="token string">'string'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selectorOrArray<span class="token punctuation">)</span>
    <span class="token comment">/* 如果是数组说明是通过.find返回的。就直接返回该数组 */</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>selectorOrArray <span class="token keyword">instanceof</span> <span class="token class-name">Array</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> selectorOrArray
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
        <span class="token comment">/* 获取之前操作的元素 */</span>
        oldApi<span class="token operator">:</span> selectorOrArray<span class="token punctuation">.</span>oldApi<span class="token punctuation">,</span>
        <span class="token comment">/**
         * 获取当前元素的子元素，根据选择器。
         * 接收一个选择器，根据选择器获取元素组成的数组，
         * 将它们追加到一个新的数组中，并在返回的 jQuery 中传入这个数组。
         */</span>
        <span class="token function">find</span><span class="token punctuation">(</span><span class="token parameter">selector</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">let</span> array <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">let</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token comment">/* 此处 Array.from 表示将伪数组转为数组 */</span>
                <span class="token keyword">const</span> childElements <span class="token operator">=</span> Array<span class="token punctuation">.</span><span class="token function">from</span><span class="token punctuation">(</span>elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selector<span class="token punctuation">)</span><span class="token punctuation">)</span>
                <span class="token comment">/* concat 表示数组中追加项(可以是一个或多个) */</span>
                array <span class="token operator">=</span> array<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>childElements<span class="token punctuation">)</span>
            <span class="token punctuation">}</span>
            <span class="token comment">/* 在数组中存储之前的this */</span>
            array<span class="token punctuation">.</span>oldApi <span class="token operator">=</span> <span class="token keyword">this</span>
            <span class="token keyword">return</span> <span class="token function">jQuery</span><span class="token punctuation">(</span>array<span class="token punctuation">)</span>
        <span class="token punctuation">}</span><span class="token punctuation">,</span>
        <span class="token function">end</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token comment">/* 此处的this.oldApi就是之前操作的this */</span>
            <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>oldApi <span class="token operator">?</span> <span class="token keyword">this</span><span class="token punctuation">.</span>oldApi <span class="token operator">:</span><span class="token keyword">this</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="实现-get-、each-、parent-、children"><a href="#实现-get-、each-、parent-、children" class="header-anchor">#</a> 实现 <code>get()</code>、<code>each()</code>、<code>parent()</code>、<code>children()</code></h2> <p>代码</p> <div class="language-js extra-class"><pre class="language-js"><code>window<span class="token punctuation">.</span><span class="token function-variable function">jQuery</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">selectorOrArray</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">let</span> elements
    <span class="token comment">/* 判断 selectorOrArray 如果是字符串说明是选择器，就根据选择器做dom处理 */</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">typeof</span> selectorOrArray <span class="token operator">===</span> <span class="token string">'string'</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelectorAll</span><span class="token punctuation">(</span>selectorOrArray<span class="token punctuation">)</span>
    <span class="token comment">/* 如果是数组说明是通过.find返回的。就直接返回该数组 */</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>selectorOrArray <span class="token keyword">instanceof</span> <span class="token class-name">Array</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        elements <span class="token operator">=</span> selectorOrArray
    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
        <span class="token function">get</span><span class="token punctuation">(</span>index<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">return</span> elements<span class="token punctuation">[</span>index<span class="token punctuation">]</span>
        <span class="token punctuation">}</span><span class="token punctuation">,</span>
        <span class="token comment">/* 循环当前元素组成的数组 */</span>
        <span class="token function">each</span><span class="token punctuation">(</span><span class="token parameter">fn</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>fn<span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token keyword">let</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> elements<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
                    <span class="token function">fn</span><span class="token punctuation">.</span><span class="token function">call</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">,</span> elements<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span>
                <span class="token punctuation">}</span>
            <span class="token punctuation">}</span>
            <span class="token keyword">return</span> <span class="token keyword">this</span>
        <span class="token punctuation">}</span><span class="token punctuation">,</span>
        <span class="token comment">// 获取当前元素的父元素</span>
        <span class="token function">parent</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">const</span> array <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span>
            <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">each</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">node</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
                <span class="token keyword">if</span><span class="token punctuation">(</span>array<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span>node<span class="token punctuation">.</span>parentNode<span class="token punctuation">)</span> <span class="token operator">===</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                    array<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>node<span class="token punctuation">.</span>parentNode<span class="token punctuation">)</span>
                <span class="token punctuation">}</span>
            <span class="token punctuation">}</span><span class="token punctuation">)</span>
            <span class="token keyword">return</span> <span class="token function">jQuery</span><span class="token punctuation">(</span>array<span class="token punctuation">)</span>
        <span class="token punctuation">}</span><span class="token punctuation">,</span>
        <span class="token function">children</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">const</span> array <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span>
            <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">each</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">node</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
                <span class="token comment">/* if(array.indexOf(node.parentNode) === -1) {
                    array.push(...node.children)
                } */</span>
                array<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span><span class="token operator">...</span>node<span class="token punctuation">.</span>children<span class="token punctuation">)</span>
            <span class="token punctuation">}</span><span class="token punctuation">)</span>
            <span class="token keyword">return</span> <span class="token function">jQuery</span><span class="token punctuation">(</span>array<span class="token punctuation">)</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="实现-appendto"><a href="#实现-appendto" class="header-anchor">#</a> 实现 <code>appendTo()</code></h2> <p>and...</p> <h2 id="命名风格"><a href="#命名风格" class="header-anchor">#</a> 命名风格</h2> <p>通过jQuery获取的对象要使用$开头的变量获取，以便于普通的变量区分</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> $div <span class="token operator">=</span> <span class="token function">$</span><span class="token punctuation">(</span><span class="token string">'.test'</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">'.item'</span><span class="token punctuation">)</span>
</code></pre></div><h3 id="拓展"><a href="#拓展" class="header-anchor">#</a> 拓展</h3> <p><code>Array.from()</code> 表示对数组(或伪数组)做进一步处理，语法：</p> <div class="language-js extra-class"><pre class="language-js"><code>console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>Array<span class="token punctuation">.</span><span class="token function">from</span><span class="token punctuation">(</span><span class="token string">'foo'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 输出: Array [&quot;f&quot;, &quot;o&quot;, &quot;o&quot;]</span>

console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>Array<span class="token punctuation">.</span><span class="token function">from</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">+</span> x<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 输出: Array [2, 4, 6]</span>
</code></pre></div><p><code>Array.prototype.concat()</code> 表示数组拼接(参数可以是单个项或数组)，语法：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">const</span> array1 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> array2 <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">'d'</span><span class="token punctuation">,</span> <span class="token string">'e'</span><span class="token punctuation">,</span> <span class="token string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> array3 <span class="token operator">=</span> array1<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>array2<span class="token punctuation">)</span><span class="token punctuation">;</span>

console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>array3<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 输出: Array [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;d&quot;, &quot;e&quot;, &quot;f&quot;]</span>
</code></pre></div><br> <p style="text-align:center;">- end -</p></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">上次更新：</span><span class="time">2021-02-10 12:44</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev"><svg aria-hidden="true" class="icon"><use xlink:href="#icon-left"></use></svg> <a href="/docs/js/base/dom-operate-across-threads.html" class="prev">DOM 操作跨线程</a></span> <span class="next"><a href="/docs/js/base/plugin.html">JavaScript 插件 / 库</a> <svg aria-hidden="true" class="icon"><use xlink:href="#icon-right"></use></svg></span></p></div> </main></div><div class="global-ui"><!----><!----></div></div>
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